The present invention relates to a portable information processing apparatus that has a main body, on the upper face of which is a keyboard, and a lid, which has provided on an internal surface a liquid crystal display panel and which is hinge coupled with the rear edge of the main body so as to be rotatable relative to the main body; and to a stand on which such a portable information processing apparatus is mounted. In particular, the present invention pertains to a portable information processing apparatus that, by using a liquid crystal display panel as a projection transparency, can be employed with an overhead projector (an OHP device); and to a stand for such a portable information processing apparatus. More specifically, the present invention relates to a portable information processing apparatus that can be employed with an OHP device while the main body and the lid remain coupled together, and to a stand for a portable information processing apparatus.
In line with current technical advances, increasing use is being made of compact personal computers (also called portable computers, or notebook computers) whose light-weight construction is indicative of the influence portability considerations had in their design.
A specific example of a notebook computer 1 is shown in FIG. 1. This example is almost identical to the ThinkPad 755CE/755CSE/755CD, which is a computer that is sold by IBM Japan, Ltd. In FIG. 1, the notebook computer 1, which is a so-called "structure with a lid," includes a thin main body 10 and a lid 50 that is so coupled with the main body 10 that it can be freely opened and closed.
The main body 10 has a shallow case 11 and a keyboard 12 that serves as an input device. A system board that is constituted by a CPU, a RAM, a ROM and a system bus, an external storage device, such as an HDD or a CD-ROM, and a battery pack (none of them shown) are incorporated in the case 11. The keyboard 12 serves as the upper face of the case 11 and also shields the inside.
The lid 50 includes a shallow rear cover 51, a liquid crystal display panel 52 that serves as a display device, and a front bezel 53 that secures the liquid crystal display panel 52. A pair of tongue pieces 54a and 54b, which have a nearly cylindrical shape, are integrally formed at the lower end of the front bezel 53. As the tongue pieces 54a and 54b are hinge coupled with corresponding portions of the main body 10, the lid 50 is hinged on the main body 10 so as to be rotatable relative to the main body 10. The liquid crystal display panel 52 is a thin display assembly wherein multiple liquid crystal devices are arranged. Since the liquid crystal display panel 52 does not itself emit light, a back light (not shown), which highlights display contents, and a light diffusion plate (not shown), which diffuses irradiated light and provides a uniform light intensity for the whole screen, are provided on the reverse face of the liquid crystal display panel 52. Drivers (not shown) along the X axis and the Y axis, which drive the liquid crystal display panel 52, are provided in the lid 50 that is shielded by the front bezel 53 and the rear cover 51.
As notebook computers are easily carried and are used in various places, and as the needs of users vary, various modes for the use of notebook computers are accordingly employed. The use of a notebook computer as an auxiliary presentation means is one of the most specific examples. In this case, members on the reverse side of the liquid crystal display panel (the rear cover and the light diffusion plate) are removed to permit the through transmission of light, and, in place of a projection transparency (foil), the liquid crystal display panel is so mounted on the light source portion of an overhead projector (OHP device) that an enlarged image of the display screen can be directly projected onto a screen. The advantages derived from such an application with an OHP device are as follows:
Advantage 1:
Since a display screen that is driven by the computer is used, a projection transparency is not required. In addition, as the contents of a display can be prepared and edited with a computer, during a presentation the display contents can be constantly updated (added to, deleted, or corrected) as needed. Further, since the display contents are ordinarily stored in advance in the memory of a computer or in an external storage device, such as an HDD or an FDD, and there is thus no increase in the amount of reference material that is needed for a presentation, even if the number of display screens is increased, it is easy to carry the reference material.
Advantage 2:
Since the screen data that are displayed on a liquid crystal display panel can be scrolled, or a new page can be displayed by key input (for example, with a cursor key), switching of the matter displayed on an OHP screen is facilitated. Further, since what is displayed can be controlled with a computer, the storing, transporting and arranging of the display contents are easy, and the order in which data are to be displayed will not be mixed up.
Advantage 3:
Some recent computers have included video capture controllers that can process analog video signals and a CD-ROM drive that can store video image data, and can thus display video images. It is therefore possible to project animated images onto an OHP screen by displaying a video image on the liquid crystal display panel.
Such use modes for notebook computers provide the following effects for a presenter. Specifically, the advanced graphic function of a computer can be fully employed, and presentation material can be prepared directly (the word "directly" here means that ordinary procedures, such as the printing of prepared data and the copying of data to a transparency, are not required). Again, as the material that is projected onto an OHP screen can be changed by the key operation, a presentation can be given smoothly. Since a presenter is not distracted by manually exchanging transparencies, he can concentrate all his attention on giving his presentation. Another plus factor is that the attention of the audience can be drawn to the OHP screen by displaying video images on it. And an associated benefit that is also appreciated by a presenter is that the preparation of transparencies, which requires much time, can be eliminated.
For the audience, the following effect can be provided. Since projected images can be switched instantaneously and smoothly, audience's concentration can be continuously ensured. The on and off display of video images on an OHP screen not only helps an audience to understand the contents of a presentation, but is also very visually attractive.
Therefore, it is not too much to say that the employment of notebook computers with OHP devices can provide improved and innovative styles and methods for conventional presentations, which are given at meetings of companies and other associations, and at academic meetings and other symposiums, and that are employed for lectures at universities and other schools.
To employ a notebook computer with an OHP device, it is necessary to solve several problems.
Problem 1:
One of the problems concerns the mounting of a liquid crystal display panel on an OHP light source, i.e., the installment. Disclosed in Japanese Unexamined Utility Model Publication No. Sho 64-121 is a lid, which includes a liquid crystal display panel, that can be removed from a main body at the hinge at its rear edge so that it is possible to mount only the lid on an OHP light source section. Disclosed in Japanese Unexamined Patent Publication No. Hei 03-1184 is a design that permits the removal of only a liquid crystal display panel, while the frame of a lid is retained in place, so that the panel can be mounted on an OHP light source section. Further, disclosed in Japanese Unexamined Patent Publication No. Hei 03-282441 is a design that instead of permitting the removal of a liquid crystal display panel from a main body, provides for the mounting on an OHP light source section of an expansion liquid crystal display panel.
When, according to Japanese Unexamined Utility Model Publication No. Sho 64-121 and Japanese Unexamined Patent publication No. Hei 03-1184 and No. Hei 03-282441, only a flat liquid crystal display panel is mounted on an OHP light source section, as the center of gravity is comparatively stable, there is no fear of the panel falling and the problem concerning installation can be ignored.
However, when, according to the descriptions given in these publication documents, liquid crystal display panels are provided that can be separated from computer bodies, since the cables that carry the RGB signals that are required for comparatively high speed performance must be extended from the main body to the liquid crystal display panel, the influence of electromagnetic interference (EMI) can not be avoided. In addition, in the notebook computer that is disclosed in Japanese Unexamined Utility Model Publication No. Sho 64-121, the hinge portion must not only support the main body and the cover, but must also permit it to be detachable and must further support a mechanism that passes through the cables. Thus, it can be assumed that an actual structure will be complicated. With the design that is disclosed in Japanese Unexamined Patent Publication No. Hei 03-1184, after a liquid crystal display panel is removed, it does not seem that the connection of a cable and a connector will be as easy as is shown in the diagrams. And with the design that is described in Japanese Unexamined Patent Publication No. Hei 03-282441, a user would be charged more for the expansion liquid crystal display panel. In short, systems that only liquid crystal display panels to be is mounted on OHP light source sections can not be realized as easily as would be anticipated from the drawings included in the individual publication documents. In FIG. 4 of German Unexamined Patent Publication No. 4019755, 1992 is disclosed a main body and a liquid crystal display panel that are not separated from each other, and that, with a lid opened until it is almost horizontal, are both mounted on an OHP light source section. The problems that arise from the removal of a liquid crystal display panel and the extension of RGB signal lines can thereby be eliminated. Many OHP devices that are currently available on the market, however, do not have a large enough foot print to permit the mounting on them of both a liquid crystal display panel and a keyboard (main body). To implement this patent publication, not only the notebook computer but also a specially ordered OHP device must be prepared, making this system unsuitable general application. Also in Japanese Unexamined Patent Publication No. Hei 04-16824 is disclosed a design whereby the entire main body of a computer is mounted on an OHP light source section. More specifically, while a lid (a liquid crystal display panel) is open and is perpendicular to the main body, a recessed portion, which is integrally formed with the main body, engages one end of an OHP light source section and is installed. The OHP device disclosed in this publication is employed with a specific computer, and is, as it were, a specially ordered device. The main body (keyboard) of a computer that stands upright would interrupt the view of the audience, so that they could scarcely see an OHP screen.
It is not realistic for computer makers to develop optical devices that can be used only with the products of a specific company, as in German Patent Publication No. 4019755, 1992, and Japanese Unexamined Patent Publication No. Hei 04-16824. It is preferable that OHP devices that are available on the market be employed for such applications.
Problem 2:
Another problem is the positioning of a liquid crystal display panel relative to an OHP light source section in the direction of height.
To use a computer with an OHP device, a liquid crystal display panel is set parallel to the glass surface of the OHP light source section. A liquid crystal display panel that is used for a notebook computer has, at most, a diagonal dimension of about 10.4 inches, whereas the glass surface of a general OHP light source section, at 11.times.11 inches, is a size larger. Thus, when the liquid crystal display panel is positioned a small distance above the OHP light source section, more light is gathered on the display panel and a brighter image can be projected onto a screen.
When the main body and the lid are positioned with the lid open and almost horizontal to the main body, as in German Patent Publication No. 4019755, this positioning is preferable because the liquid crystal display panel is separated from the OHP light source section only by a distance that is equivalent to the thickness of the main body. However, with a computer model that has a thick main body, the liquid crystal display panel will be positioned too high and outside the focusing range of an OHP light source section, and an image that is projected onto a screen will be blurred. Since it incorporates a CD-ROM drive, the ThinkPad 755CD that is sold by IBM Japan Ltd., for example, which has a thick main body of about 3.7 mm, is outside the a focusing range of an OHP device.
The height of a liquid crystal display panel relative to an OHP light source section is determined by obtaining a balance between the light collection and the focusing range. Through experience, it has been determined that 2 to 3.5 cm is an appropriate height for a liquid crystal display panel that is to be used with many current OHP devices.
Problem 3:
In those cases where liquid crystal display panels are not detachable and entire bodies are mounted on OHP light source sections, problems arise concerning the effect of radiation heat on the main body and on key input operations.
When the liquid crystal display panel is not detachable from the main body and the entire body is mounted on the OHP light source section, the body is directly exposed to radiation heat from the light source. If an OHP device has a comparatively low power of about 600 W, natural heat release will solve this matter. However, when a computer is mounted on an OHP device that has high power of about 1000 W and high light intensity, it is expected that the computer body will be subjected to temperatures that are much higher than those that are encountered during normal use. As a result, circuits (especially those for a CPU that itself easily generates heat) on a system board that is provided inside the main body may run away.
When a main body is set perpendicular to an OHP light source section and is installed as is disclosed in Japanese Unexamined Patent Publication No. Hei 04-16824, the problem due to the radiation of heat can be solved. It is, however, difficult for a presenter to input data during a presentation by using the keys of a keyboard which is set upright. Further, as is mentioned previously, the main body interfere the view of an audience.
When only a liquid crystal display panel is mounted on an OHP light source section, as in Japanese Unexamined Utility Model Publication No. Sho 64-121 and Japanese Patent Publication No. Hei 03-1184 and No. Hei 03-282441, the main body can be positioned at an arbitrary location so that it is not exposed to radiation heat, and the problem concerning key input does not arise. However, such solution cause other problems as already described.
There is also a proposal that calls for the attaching of a cooling fan to a notebook computer. The addition of devices and other items, however, heads to an increase in the size of a computer and reduces any cost advantage.
Problem 4:
When members on the reverse of a lid are removed, an electrically active portion, such as a backlight, is exposed externally, and a user may touch it accidentally. Further, when a liquid crystal display panel is employed with an OHP device, it is not necessary for the backlight to keep lighting place, and, further, the electricity consumed by it merely causes a waste of power. None of the publications described above, however, points out this problem.